According to this article, "a 1936 book called Typewriting Behavior" made "comparisons of the new keyboard to a jeep and the old one to an ox".

Jeeps were invented in 1941. Some origin theories of the name date back as far as WW I (but for recruits, not vehicles). If the author truly used this comparison in 1936 it would be a tremendous citation for the word's origin.

Or perhaps the comparison was made in a later edition of the book. Don't know.